start tapl/ dir

tapl/stlc-tests.rkt

@@ -0,0 +1 @@
+#lang s-exp "stlc.rkt"

tapl/stlc.rkt

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+#lang racket/base
+(require
+  (for-syntax racket/base syntax/parse))
+  
+;; Simply-Typed Lambda Calculus
+;; - one arg lambda
+;; - var
+;; - binary app
+;; - binary +
+;; - integers
+
+(define-syntax (datum/tc stx)
+  (syntax-parse stx
+    [(_ . n:integer) (⊢ (syntax/loc stx (#%datum . n)) #'Int)]
+    [(_ . x)
+     #:when (type-error #:src #'x #:msg "Literal ~a has unknown type." #'x)
+     (syntax/loc stx (#%datum . x))]))

tapl/typecheck.rkt

@@ -0,0 +1,3 @@
+#lang racket/base
+
+;; general type checking utility functions